1. Field of the Invention
The present invention relates to a knee protection air bag apparatus including an air bag which can be developed and expanded by charging expansion gas therein and can protect the knees of an occupant seated.
2. Related Art
Conventionally, as an air bag apparatus for protecting the knees of an occupant, there is known an air bag apparatus in which an air bag cover including a lid part and a general part with its periphery surrounded by the interior member of a vehicle is assembled to a case, which stores therein a folded air bag and an inflator and is mounted on and fixed to the body of the vehicle, such that the air bag cover is movable in three directions, that is, in the vertical direction, in the right and left direction and in the back-and-forth direction so as to be able to absorb an assembling error (for example, see Japanese Patent Publication JP 2003-205814A).
And, there is also known another air bag apparatus in which an air bag cover is structured such that the upper side portion of the air bag cover is secured to a case movably in the vertical direction, in the right and left direction and in the back-and-forth direction in such a manner as to be able to absorb an assembling error, while the lower side portion of the air bag cover is positioned such that the movement thereof in the back-and-forth direction is prevented, whereby the air bag cover can be prevented from wobbling in the back-and-forth direction (for example, see Japanese Patent Publication JP 2004-106560A).
In this type of air bag apparatus for protection of the kneels of an occupant, since the air bag cover including the lid part and the general part with its periphery surrounded by the interior member of the vehicle is movably assembled to the case which stores therein the folded air bag and the inflator and is mounted on and fixed to the body of the vehicle, when the air bag is expanded and developed, the air bag cover is pushed to the rear side of the vehicle by the expanding air bag and thus the moving amount of the air bag cover to the vehicle rear side increases, thereby weakening the breaking stress that the lid part of the air bag cover receives from the expanding air bag; and, depending on the assembled state of the air bag cover and case, there can be formed a clearance between them and thus the expanded air bag can be stuck out from the clearance, thereby raising a fear that the breaking stress of the air bag cannot be transmitted to the lid part of the air bag cover sufficiently.